Investigators trying to determine what happened to missing college student Mollie Tibbetts issued a polygraph test on Tuesday to Wayne Cheney, a farmer who has been interviewed before about the case, the farmer said Thursday.

Cheney said the polygraph administrator asked him whether he had anything to do with the 20-year-old Tibbetts' disappearance, and he told them no. He told Fox News on Thursday that he doesn't know the results of his polygraph exam.

The polygraph was issued in Brooklyn, Iowa, just a day after Cheney told the Des Moines Register that he wouldn't take the test even though he has "nothing to hide."

Authorities have shared few details about their investigation, now in its third week, but social media chatter has given prominence to the FBI's search of Cheney's property and his repeated interactions with authorities.

State officials canceled a news conference planned for Tuesday, saying they had nothing to share and postponed a conference scheduled for Friday until Monday.

Authorities are asking anyone with information about Tibbetts' disappearance to contact the Poweshiek County Sheriff’s Office at 641-623-5679 or tips@poweshiekcosheriff.com.

More than $300,000 has been raised from donors across the country as a reward to solicit information that assists in her safe return.